Arbuscular mycorrhizal fungi as mediators of ecosystem responses to nitrogen deposition: A trait‐based predictive framework

Abstract

2. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community.As a result, the remaining AMF taxa may confer less P benefit to their host plants.3. Using a synthesis of data from the literature, we found that the ability of a taxon to persist in the face of increasing soil N availability was particularly high in isolates from the genus Glomus, but especially low among the Gigasporaceae. Across AMF genera, our data support the prediction that AMF with a tolerance for high soil N may confer a lower P benefit to their host plant. Relationships between high N tolerance and production of external hyphae were mixed. Synthesis.If the relationship between N tolerance and plant P benefit is widespread, then shifts in arbuscular mycorrhizal fungi communities associated with N deposition could have negative consequences for the ability of plants to acquire P and possibly other nutrients via a mycorrhizal pathway. Based on this relationship, we predict that arbuscular mycorrhizal fungi responses could constrain net primary productivity in P-limited ecosystems exposed to N enrichment. This prediction could be tested in future empirical and modelling studies.

The relative importance of ecological drivers of arbuscular mycorrhizal fungal distribution varies with taxon phylogenetic resolution

“…PC2 represented a strong increase in inorganic N availability but also in N : P in fields recently converted to agriculture. The turnover of closely related AM fungi along PC2 contradicts the idea that AM fungal association with N availability (plant‐available N in our case) is conserved at family or genus level (Treseder et al ., ). This discrepancy could be due to the difference in the study ecosystems (natural or agricultural ecosystems), to fungal physiological requirement (e.g.…”

“…Inferring life‐history strategies and functions in fungi remains difficult (Powell & Rillig, ; Treseder et al ., ). We show that one could infer such traits from distribution data based on DNA sequencing when coupled with contextual parameters, which is a promising result given that DNA‐based assessments of biodiversity are now accumulating.…”

“…For example, spore size and amount produced, as well as investment in extra‐ or intraradical mycelium, appear conserved at the family level (Hart & Reader, ; Maherali & Klironomos, ; Powell et al ., ; Chagnon et al ., ). Likewise, family‐ or order‐level community composition is well predicted by spatial variation in soil pH, soil phosphorus (P) and nitrogen (N) content, or soil depth (Camenzind et al ., ; Rodríguez‐Echeverría et al ., ; Roy et al ., ; Sosa‐Hernández et al ., ; Stürmer et al ., ; Treseder et al ., ), supporting a phylogenetic conservatism of niche and traits at a coarse phylogenetic resolution. On the other hand, AM fungi exhibit extensive genetic variation within morphologically (spore‐based) defined species, which can affect compatibility with their host plant (Angelard et al ., ) and traits such as extraradical hyphal density (Munkvold et al ., ; Koch et al ., ; Mensah et al ., ): the variability in these traits and the consequences for host performance were higher within than between AM fungal species.…”

Global meta‐analysis reveals different patterns of root tip adjustments by angiosperm and gymnosperm trees in response to environmental gradients

“…() also observed a significant relationship between ectomycorrhizal mantle surface area and MAT, though in this case there appeared to be greater association with the fungi in cooler climate, which is associated with lower soil fertility, rather than warmer climates. Despite the lack of relationship observed between arbuscular mycorrhizal mycelial biomass and climate among angiosperm trees (Supporting Information Figure S7b), it is still possible, even likely that arbuscular mycorrhizal fungi also play important roles as mediators regarding angiosperm responses to changes in environment (Treseder et al., ). For instance, based on 14 coexisting arbuscular mycorrhizal broadleaf (12 species) and needle (two species) tree species, Liu et al.…”

Changing perspectives on terrestrial nitrogen cycling: The importance of weathering and evolved resource‐use traits for understanding ecosystem responses to global change

“…Accordingly, biomass of the former plant lineage does not significantly respond to N addition, while the biomass of the latter increases (Wooliver et al, ). Thus, N deposition can induce plants to decrease C investment to these symbionts below‐ground, thereby decreasing biomass and abundance of these formerly beneficial microbial symbionts (Treseder et al, ) and weakening the plant–soil feedbacks that had been positive in low‐nutrient soils (Revillini, Gehring, & Johnson, ). Based on these patterns, subsequent co‐evolution between plants and their nutrient‐acquiring microbial symbionts should diminish under N deposition, and lower abundances of mycorrhizal symbionts should leave pools of more complex SOM intact.…”